I'm looking for a laser to measure the transmittance of my H-alpha filter for solar observing. The filter's bandwidth is nominally 0.05nm. It is tilt and temperature tuneable by approximately +/- 0.1nm.
The laser I'm thinking of would be at 656.28nm, or as near to that as possible, and tuneable by at least +/- 1nm. It also needs to to have a line width of < 2 GHz so that I can use a Burleigh wavemeter (Model WA-10), which gives me a resolution of 0.001nm with a laser having that kind of linewidth. My plan is to use a Coherent Labmaster Ultima-2 2-channel power meter to give me %T, and plot that versus wavelength for many settings of the filter and at a number of points in its clear aperture.
Any leads of suggestions would be greatly appreciated! Thanks in advance.
Laser Wanted
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Colin Kaminski
Laser Wanted
The Analog Technologies Laser can do everything you need. They did not have any interest and stopped selling it. They sold it as a temperature tunable laser. If you call them they might have enough parts to build one. Really this would not be to hard to build. Just get a single mode diode that is close to the frequency, say 658nm and cool it till it is on band with your filter. If I remember right the Mitsubishi diode I played with tuned .1nm per degree C. So we are only talking about 40F or so to get it on band to your filter. The wide (compared to holography) stability requirement would mean that mode hops would not be too problematic.
I have some parts around that might be helpful if you want to play with the idea. I am out of TECs and diodes but I have a few temperature and power controllers.
wler took some of my parts from my failed attempt and made a diode laser that really can make holograms. It took him a fair amount of time. Since you don't need meters of coherence it will not be as hard. He sent me the laser but it is dialed in so well that I am afraid to change the TEC temperature and I am a little higher than 656.28nm.
The other thing you could do is replicate a laser that JonathanH and I worked on 10 years ago. He lives in Canada and we used to communicate by email daily. We made a couple of lasers that were a soldered copper box that held 1L of water. Soldered to the bottom was a copper block that you could press fit a diode housing into. You filled the box with water and put in a temperature probe. You kept boiling water and Ice water around and with a little math you could calculate how much of each it took to change the temperature. Once you found the range of stability for that diode you held it as close as you could. You then stole a little of the beam and watched (or listened) for stability and adjusted the temperature till everything looked good. Then you would open the shutter and expose the hologram. Most of the time it would be modehop free.
Since you are only looking to measure a single or a few etalons that might be the cheapest and easiest route.
I have some parts around that might be helpful if you want to play with the idea. I am out of TECs and diodes but I have a few temperature and power controllers.
wler took some of my parts from my failed attempt and made a diode laser that really can make holograms. It took him a fair amount of time. Since you don't need meters of coherence it will not be as hard. He sent me the laser but it is dialed in so well that I am afraid to change the TEC temperature and I am a little higher than 656.28nm.
The other thing you could do is replicate a laser that JonathanH and I worked on 10 years ago. He lives in Canada and we used to communicate by email daily. We made a couple of lasers that were a soldered copper box that held 1L of water. Soldered to the bottom was a copper block that you could press fit a diode housing into. You filled the box with water and put in a temperature probe. You kept boiling water and Ice water around and with a little math you could calculate how much of each it took to change the temperature. Once you found the range of stability for that diode you held it as close as you could. You then stole a little of the beam and watched (or listened) for stability and adjusted the temperature till everything looked good. Then you would open the shutter and expose the hologram. Most of the time it would be modehop free.
Since you are only looking to measure a single or a few etalons that might be the cheapest and easiest route.
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Colin Kaminski
Laser Wanted
wler just posted a note that he is going to make up some laser heads. Get one with a 658nm diode and and adjust the parameters yourself. That just might be the best way and when you are done you can use it for holography.
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BobH
Laser Wanted
Thanks for the tips, Colin. I just found a Burleigh wavemeter on Ebay and spent the day realigning it. It reads directly to 0.001nm, but at 800ms per reading at its fastest.
I'd like to see a plot of transmittance versus wavelength. I have a Coherent Labmaster Ultma-2 2-channel power meter to give me transnittance via RS-232. There's a 25-pin connector with BCD for the wavelength output from the wavemeter, and timing signals too.
I'm thinking to set it up do make plots at five places in the clear aperture, at a range of specific tilt angles (I have a Newport motor driven rotation stage to use here if automation is needed), and at many temperature settings. I'm on a hunt for the ultimate filter characterization machine!
At least until the activity comes back. :boohoo:
I'd like to see a plot of transmittance versus wavelength. I have a Coherent Labmaster Ultma-2 2-channel power meter to give me transnittance via RS-232. There's a 25-pin connector with BCD for the wavelength output from the wavemeter, and timing signals too.
I'm thinking to set it up do make plots at five places in the clear aperture, at a range of specific tilt angles (I have a Newport motor driven rotation stage to use here if automation is needed), and at many temperature settings. I'm on a hunt for the ultimate filter characterization machine!
At least until the activity comes back. :boohoo: